Light-diffusing, insulating, glazing system component

ABSTRACT

A light diffusing insulating glazing insert consists of a flexible thin-walled honeycomb transparent insulation, to which is bonded a diffusing sheet, on one or both sides This provides a practical solution to problems related to utilizing thin-walled flexible honeycombs in glazing units consisting of two sheets of glass, plastic, or similar and a spacer/frame, as standard for window and skylight applications. Use of such a glazing insert adds insulation and light diffusion to the glazing system.

FIELD OF THE INVENTION

This invention relates to glazing systems such as windows, skylights,atriums, greenhouses, sunrooms and the like.

BACKGROUND OF THE INVENTION

Honeycomb transparent insulation was first developed in the early 1960'sin order to enhance the insulation value of glazed systems, with minimumloss of light transmittance. Honeycomb transparent insulation consistsof transparent-walled honeycombs, with open-ended cells whose axes areoriented parallel to the normal vector of the plane of the glazing. Thematerials transmit light by a forward-reflection process, and impedeheat transfer by suppressing convection and radiant transfer. Thesemechanisms are well understood and described in the technicalliterature. See, for example, “Coupled Radiative and conductive heattransfer across honeycomb panels and through single cells”, K. G. T.Hollands et al., Int. J. Heat Mass Transfer v.27, n.11 pp. 2119-2131,1984; “An approximate equation for predicting the solar transmittance oftransparent honeycombs”, K. G. T. Hollands, K. N. Marshall, and R. K.Wedel, Solar Energy, v.21 pp. 231-236, 1978).

Honeycomb transparent insulation is typically made from transparentplastics such as acrylic, polycarbonate, or polypropylene. These aremanufactured by a number of different techniques, including capillarybundling, extrusion, and film-fabrication. Their properties (such aslight transmittance, insulation value, rigidity, weight, etc.) stronglydepend on how they were manufactured. Examples of honeycomb transparentinsulations are lnsolCore®, a film-based transparent insulation made byAdvanced Glazings Ltd., Nova Scotia, Canada, Kapillux®, acapillary-bundled transparent insulation made by Okalux KapillarglasGmbh. of Marktheidenfeld-Altfeld, Germany, and AREL®, an extrudedtransparent insulation made by Arel Energy Ltd., Yavne, Israel.

It is often desirable to use honeycomb transparent insulation in aglazing unit, where it is mounted between two panes of glass, sheets ofplastic, or similar, taking the place of the air gap or gas layer thattraditionally provides insulation. Such glazing units can be used to letdaylight into buildings, while at the same time, providing goodinsulation. They can be used in skylights, sunrooms, atriums, or certainwindow applications, or anywhere natural light is desired but a clearview of the outdoors is not necessary or desirable. The use of suchhoneycomb transparent insulation-filled glazing units gives theadvantage of lower heat transfer (which in cold climate, causes warmerinterior surface temperature, in increased thermal comfort and lesscondensation, and in warm climates, means lower air conditioning costs),diffuse light transmittance (resulting in high-quality uniform naturallight and lower glare), and privacy.).

Rigid thick-walled honeycombs are straightforward to use in glazingunits, where they are simply sandwiched in between the two sheets ofglass. The rigidity of such transparent insulations prevents them from‘sagging’ under their own weight, when used in inclined or verticalpositions. Thus it is not necessary to fix the transparent insulation tothe frame of the glazing unit or to on or both of the glazings. Anexample of the use of a glazing unit incorporating a rigid honeycombtransparent insulation is Okalux, made by Okalux Kappilarglas Gmbh. ofMarktheidenfeld-Alffeld, Germany. This product consists of rigidcapillary-bundled honeycomb transparent insulation, covered on bothsides by a light diffusing fiberglass veil cloth, and sandwiched insidetwo pieces of clear glass, and surrounded by a spacer/frame to create aglazing unit. It is important to note that the fiberglass cloth is notbonded to the honeycomb, and is included for the purpose of diffusinglight as well as for aesthetic value.

One very important parameter in determining properties of honeycombtransparent insulations is wall thickness. It is often desirable toconstruct honeycomb transparent insulations with the minimum practicalwall thickness, because (with all other variables held constant) thisresults in minimum solid heat conduction, minimum optical losses, andmaterial cost. However, the rigidity of the honeycomb is reduced as thewalls become thinner. The range of practical wall thicknesses isdetermined to some degree by manufacturing method. The film fabricationmethod is known to be useful for making honeycomb transparentinsulations with very thin walls. Film-fabricated honeycombs areinherently flexible, and this flexibility increases as wall thicknessdecreases. For example, InsolCore, a film-fabricated transparentinsulation made by Advanced Glazings Ltd. of Nova Scotia, Canada, haswall thickness on the order of 0.001″. This flexibility can be usedadvantageously: such materials can be compressed to reduce volume whileshipping and later re-expanded; and such materials can comply to thecontours of underlying ceiling layers in ceiling-attic construction asdescribed in our co-pending application no. CA 2,254,457.

However, flexibility becomes problematic when using honeycombtransparent insulation in applications such as daylighting, where thetransparent insulation is mounted in a glazing unit between two sheetsof rigid glazing material (typically glass, or plastic such aspolycarbonate or acrylic). If a flexible honeycomb is simply sandwichedbetween glazings, as is done with rigid honeycomb transparentinsulations, it is likely to sag under its own weight, drawing away fromthe frame at one or more edge of the glazing unit. This may be caused bygravity if the glazing unit is handled or mounted in a non-horizontalposition, or it may simply happen as a result of dimensional changescaused by residual internal stresses in the honeycomb transparentinsulation itself. One solution has been to attach the honeycomb to theedge (frame) of the glazing cavity, or to one or both of the rigidglazings that define the glazing unit itself. However, such a mountingprocedure is labour-intensive and the use of adhesive to fasten ahoneycomb to a glazing results is typically aesthetically displeasing.

It is well known that honeycomb transparent insulation scatters lightand cannot transmit images at off-normal incidence. Therefore, glazingunits filled with transparent insulation cannot be used in windowapplications where preservation of view is important. But the advantagesof diffuse glazings for daylighting applications are well-known.Specifically, diffusely-transmitted light distributes throughout theinterior of a building, reducing glare and shadowing relative tospecularly-transmitted daylight. Filling the interior of a glazing unitwith honeycomb transparent insulation contributes to the diffusing powerof this glazing system. However, honeycombs are ‘conical scatterers’,that scatter incoming light over a range of azimuth angles, whilepreserving the original angle of inclination. This means that honeycombtransparent insulations have a limited ability to provide lightdiffusion at near-normal incidence angle. This also means that theytransmit images at normal incidence, and thus a glazing unit made withspecular (non-diffusing) glazings and honeycomb transparent insulationprovides incomplete privacy. This is improved by the addition of one ormore secondary diffusing layers, such as a loose-weave fibreglass clothor veil, as is known in the state of the art.

The rigidity of a honeycomb material is greatly increased by bonding asheet of material to one or both sides of the honeycomb. This principleis well-known in engineering and material science, and numerouslight-weight composite honeycomb-core structural materials exist today.Examples are door panels made from wood veneer bonded to paperhoneycombs, and high-tech plastic and metal honeycomb-core materialsused in the aircraft industry. As well, honeycomb cores, adhesives, andskinning materials are readily available throughout the supply chain ofthe composites industry. The present invention takes advantage of theaforementioned principle in order to create a rigid sandwich from aflexible, thin-walled honeycomb transparent insulation core.

SUMMARY OF THE INVENTION

According to the present invention there is provided a composite lightdiffusing insulating glazing insert characterized in that it comprises aflexible thin-walled transparent honeycomb insulating core layer (10)defining a plurality of honeycomb cells, and a flexible skinning layer(18) bonded to each major surface of said core layer, each said flexibleskinning layer having sufficient tensile and compressional stress tohold its own shape over dimensions in the order of the size of saidcells whereby said composite glazing insert is substantially rigid.

The glazing insert may be in the form of honeycomb transparentinsulation in glazing systems to create a light-diffusing, insulatinginsert that can be sandwiched between sheets of glass, plastic, or thelike.

The skinning layer can be bonded to one or both sides of the insulationby means of an adhesive or by a heat-seal. The resulting coveredhoneycomb can be used as a diffusing, insulating glazing insert. Theskinning layer may be a cloth, mesh, mat, veil, paper, or film, madefrom fiberglass, plastic, natural fiber, or other material.

This invention offers most of the benefits of transparent insulationitself, but also offers two additional advantages. First, the inventionprovides a practical way to utilize a thin-walled flexible honeycombtransparent insulation as an insulating and diffusing insert in glazingunits. Second, it also provides a way to rigidize a thin-walledhoneycomb transparent insulation material, so that it can hold its owndimensions prior to, and following, installation in a glazing unit. Suchan insert can be used in the manufacture of diffuse insulating glazingunits, in the same way as rigid transparent insulations, avoiding theproblem of sag or dimensional changes inherent in the use of thin-walledflexible transparent insulations. It achieves this without the necessityof bonding the thin-walled flexible transparent insulation to theglazings or frame.

By use of this invention, the overall optical properties of thediffusing insulating glazing insert can be controlled through use ofappropriate skinning layer(s). This can be used advantageously inseveral ways:

(a) Overall light transmittance of the insert can be reduced below thatof the transparent insulation itself, as is often desirable to avoidexcessive brightness in sunrooms or atriums. If a dense diffusingskinning layer is used, the insert will have lower overall lighttransmittance, than if a sparse high-transmittance skinning layer wasused.

(b) The use of a diffuse skinning layer results in an insert withincreased light diffusing power, relative to the transparent insulationitself.

(c) The use of a diffuse skinning layer results in an insert withenhanced privacy protection, relative to the honeycomb transparentinsulation itself.

It is also possible to alter the thermal characteristics of thetransparent insulation by using an appropriate skinning layer. Inparticular, the use of indium-tin-oxide coated fibreglass clothdiffusing layer or any similar cloth, film, or similar material that haslow emissivity and high scattering or reflectivity in the thermalinfrared, can enhance the insulation value of this invention.

The invention also provides a method of making a rigid light diffusinginsulating glazing insert, characterized in that a flexible skinninglayer is bonded to each major surface of a flexible thin-walledtransparent honeycomb insulating core layer defining a plurality ofhoneycomb cells, each said flexible skinning layer having sufficienttensile and compressional stress to hold its own shape over dimensionsin the order of the size of said cells so that said composite glazinginsert becomes substantially rigid.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a honeycomb transparent insulation;

FIG. 2A shows a flexible thin-walled honeycomb transparent insulationwith a diffusing layer one side, and FIG. 2B shows the diffusing layerbonded to both sides; and

FIG. 3 illustrates an apparatus for continuously applying skin tothin-walled flexible honeycomb transparent insulation.

DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS

In FIG. 1, the honeycomb transparent insulation 10 lies in a plane 12.The axes 14 of the honeycomb cells 16 lie normal to this plane. As shownin FIGS. 2A and 2B, skinning layer 18 is bonded to one or both sides ofthe honeycomb insulation 10.

The core material 10 consists of a thin-walled flexible honeycombtransparent insulation. Honeycomb transparent insulation refers tohoneycomb material with cells whose axes are parallel to the normalvector of the major plane of the honeycomb (i.e. the plane of theglazing). In order to transmit light the walls of the honeycomb must benon-absorbing to visible and or solar wavelengths. Typically, suchnon-absorbing walls are transparent; however, they may also bereflective. The walls may or may not scatter light to some degree, andif they do scatter light, the honeycomb may have a reduced lighttransmittance due to backscattering. This lower transmittance may or maynot be an intentional feature of the honeycomb transparent insulation.However, any similar light-transmitting honeycomb material, that ispartially flexible in nature, embodies the spirit of the invention.

The skinning layer or layers 18 may consist of any sheet material thattransmits light to some degree, and preferably, but not necessarily,diffuses light. Examples are: fibreglass veil, mat, or cloth, paper,plastic film, natural fibre cloth, veil, or mat, and plastic cloth, veilor mat. The sheet may be white or coloured, in order to achieve desiredaesthetics. In order to provide the necessary rigidity in final form,the skinning layer should have sufficient tensile and compressionalstrength to hold its own shape, over dimensions on the order of a cellsize of a honeycomb (typically <0.4″). It is important to note that theskinning layer will be held in-plane by both the edges of the honeycombcells to which it is bonded, and the sheet glazing which presses againstthe glazing insert in actual application. This helps prevent bucklingunder when a sheet is under compressional loading due to bending. Inpractice, this means that very thin sheet materials can add sufficientrigidity, including the thinnest fibreglass veil cloth.

Bonding can be by adhesive or heat-sealing techniques. Heat-sealingoffers the advantage that no extra material is required, but it is morerestrictive with respect to the materials that may be used.

Adhesive bonding technique requires that the adhesives can be appliedeither to the skinning layer, or alternatively, to the edges of thehoneycomb. Following this technique, the honeycomb and skinning layerare pressed together and the glue is allowed to cure. Applying adhesiveto the skinning layer requires much more adhesive, but guarantees a moreuniform appearance. Applying adhesive to the edges of the honeycomb isvery efficient with adhesive, because adhesive is applied only whereneeded. But the adhesive can leave visible marks the contact areas, andthis has the potential to create aesthetically-displeasing appearance.Such marking can be avoided through appropriate choice of skinningmaterial and adhesive.

A wide range of adhesives are suitable for this invention, includingwater-based polymer formulations, solvent-based polymer formulations,starch-based formulations, 2-part formulations such as epoxies,polyesters, polyurethanes, or UV-curing. A suitable adhesive should havesufficient strength, good UV resistance, resistance to colour change,and clarity. If adhesive is applied to the surface of the honeycomb, anappropriate gelling agent such as fumed silica should be added to theadhesive so that it can form a stable bead at the end of the cell wall,prior to application.

To bond by heat sealing, the skinning layer is heated above the meltingtemperature of the plastic honeycomb, and pressed onto the surface ofthe honeycomb layer. Heating and pressing may be done sequentially or atthe same time. This can be accomplished in a batch process, by placingthe skinning material on a heated surface, bringing the honeycomb incontact with the heated skinning material, and removing the honeycombonce the heat-bonding has taken place. It can also be done in acontinuous process, as shown in FIG. 3, by bringing the skinninglayer(s) and honeycomb in contact with each other, between two rolls, atleast one of which is heated, and which are kept at a spacing that willcreate the necessary compression. The process can work equally well ifheated rolls are replaced with non-rotating cylinders, plates, orsimilar, as long as other means are provided to pull the materialsthrough the pinch point. In order to use the heat-sealing process, theskinning layer must be stable at temperatures above the melting point ofthe plastic honeycomb. Various fibreglass materials, including veil,mat, roving, etc. are highly compatible with this technique.

The skinning layer can be adhesive-bonded or heat-bonded.

One embodiment of an adhesive-bonded diffuse insulating glazing insertis made from a layer of InsolCore transparent insulation (AdvancedGlazings Ltd., North Sydney, Nova Scotia). The top of this honeycomb iscoated with a layer of water-based acrylic adhesive (Alpha 8010, AlphaSystems, Elkhart Indiana) to which 3% Cabosil M-5 fumed silica (CabotCorp. Mass) has been added in order to ‘gel’ it. A layer of standardfibreglass veil mat, 0.010,″ thick (commonly available through anyfiberglass products supplier) is pressed onto the honeycomb, and theadhesive is allowed to cure. The second side is covered similarly, andthe result is a rigid, light weight, diffusing insulating glazinginsert.

One embodiment of a heat-bonded diffuse insulating glazing insert ismade from a layer of InsolCore transparent insulation (Advanced GlazingsLtd., North Sydney, Nova Scotia Canada). Standard fibreglasschopped-strand mat, ¾ oz per sq.ft., 0.020″ thick (commonly availablethrough any fiberglass products supplier) is bonded to both sides of theInsolCore. The bonding is accomplished by laying the fibreglasschopped-strand mat on an aluminum plate that is heated to approximately500° F., and then pushing the honeycomb onto the heated fibreglasschopped-strand mat with light pressure just sufficient to achievebonding, and then quickly removing the skinned honeycomb from the heatedplate.

FIG. 3 illustrates a suitable manufacturing technique. Skinning layer 18is removed from stock rolls 20, and heated as it wraps around heateddrive rolls 22. Honeycomb transparent insulation is drawn through gap 24between heated drive rolls 22. Bonding takes place at the pinch point.

In another preferred embodiment of the invention, a heat-bonded diffuseinsulating glazing insert is made from a layer of lnsolCore(r)polypropylene transparent insulation (Advanced Glazings Ltd., NorthSydney, NS Canada). In this embodiment a fiberglass chopped-strand‘surfacing veil’ (Duraglass 8120, Johns Manville Corp., Toledo, Ohio) isbonded to both sides of the polypropylene layer. To bond the veil to thetransparent insulation, the transparent insulation is first laid flat ona table, and the veil is laid on top of the transparent insulation. Aheated roller, made from 3″ diameter steel pipe covered in a standardTeflon™ non-stick coating with a radiative heating element runningthrough the centre, is rolled over the top of the veil to heat-seal theveil to the surface of the transparent layer of the honeycomb material.

The transparent insulation is then flipped over, a veil laid on theopposite surface, and bonding is achieved in the same way. Good resultswere obtained with roller temperature of 450° F. (232° C.) and a rollingspeed of 2 ft/minute (60 cms/min).

In order to control the thickness of the final product, a metal spacerwas laid on the table, along either side of the honeycomb. The spacerheight is slightly smaller than the height of the honeycomb (a spacerheight of 2.480″ (6.3 cms.) worked well with the 2.5″ (6.35 cms.) thickhoneycomb). This precisely limits the depth to which the rollercompresses the honeycomb transparent insulation when it is softened bythe heat of the roller.

The process can work equally well if the heated rolls are replaced withnon-rotating cylinders, plates, or the like, as long as other means areprovided to pull the materials through the pinch point.

What is claimed is:
 1. A glazing system comprising a composite lightdiffusing insulating glazing insert sandwiched between two rigidtransparent panes, said composite light diffusing glazing insertcomprising a flexible transparent honeycomb insulating core layerdefining a plurality of honeycomb cells, said honeycomb insulating corelayer being sufficiently thin-walled that it sags under its own weight,and a flexible skinning layer bonded to each major surface of said corelayer, each said flexible skinning layer having sufficient tensile andcompressional stress to hold its own shape over said cells whereby saidflexible skinning layers rigidize said honeycomb insulating core layer.2. A glazing system as claimed in claim 1, wherein each said skinninglayer is bonded to said core layer by adhesive or heat sealing.
 3. Aglazing system as claimed in claim 1, wherein each said skinning layeris selected from the group consisting of; veil, mat, roving, glasscloth, plastic cloth, natural fiber cloth, plastic film, and paper.
 4. Aglazing system as claimed in claim 1, wherein said transparent corelayer also diffuses light.
 5. A composite light diffusing insulatingglazing insert comprising a flexible honeycomb insulating core layerdefining a plurality of honeycomb cells, and a flexible skinning layerbonded to each major surface of said core layer, each said flexibleskinning layer having sufficient tensile and compressional stress tohold its own shape over the dimensions of said cells whereby saidcomposite glazing insert is substantially rigid, and wherein each saidskinning layer is indium-tin-oxide coated fibreglass.
 6. A rigidlight-diffusing glazing system as claimed in claim 1, wherein said corelayer is made of polypropylene.
 7. A method of making a glazing systemcomprising: a) fabricating a composite rigid light diffusing insulatingglazing insert by attaching a flexible skinning layer to each majorsurface of a flexible transparent honeycomb insulating core layerdefining a plurality of honeycomb cells, said honeycomb insulating corelayer being sufficiently thin-walled that it sags under its own weight,and each said flexible skinning layer having sufficient tensile andcompressional stress to hold its own shape over the dimensions of saidcells so that said flexible skinning layers rigidize said honeycombinsulating core layer, and b) sandwiching said composite rigid lightdiffusing insulating glazing insert between two transparent panes.
 8. Amethod as claimed in cairn 7, wherein said skinning layer is sealed tosaid core layer by passing said core between rollers.
 9. A method asclaimed in claim 8, wherein said rollers are hot rollers and each saidskinning layer is heat-sealed to said core layer.
 10. A method asclaimed in claim 9, wherein said skinning layer is bonded to the corelayer with an adhesive.
 11. A method as claimed in claim 7, wherein saidcore layer is first laid flat on a supporting surface, a first saidskinning layer is applied to a first major surface of said core layer, aheated roller is applied to said first said skinning layer to bond saidfirst said skinning layer to said first major surface, said core layeris flipped over, a second said skinning layer is applied to a secondmajor surface of said core layer, and a heated roller is applied to saidsecond skinning layer on said second major surface to bond said secondskinning layer to said second major surface.
 12. A method as claimed inclaim 11, wherein a spacer is provided around said core layer to limitthe compression of the core layer during application of said heatedroller.
 13. A method as claimed in claim 12, wherein said core layer ismade of polypropylene.